Dual band infrared (IR) detectors have been made using HgCdTe, quantum well infrared photo-detectors (QWIPs), and Type II superlattice (T2SL) materials. HgCdTe detectors have high performance, and although significant progress has been made in the development of HgCdTe detectors for MW (medium wavelength)/LW (long wavelength), LW1/LW2, and MW1/MW2 dual-band detectors, HgCdTe based infrared detectors have high cost and are difficult to scale to large detector arrays. QWIPs and InAs/GaSb T2SL detectors have the disadvantage of ˜10-100 times higher dark current as compared to HgCdTe. InAs/GaSb T2SL detectors have low minority carrier lifetimes which prevent FPA (focal plane array) operation at temperatures greater than 150 Kelvin.
Elevated temperature operation is essential for large format FPAs in order to minimize the size, weight and power footprint of an infrared (IR) imaging system.
In the prior art, InAsSb-based single-band/single color devices are described by Maimon and Wicks, Appl. Phys. Lett. 89 151109 (2006). Lee et al., “Subband transitions in dual-band n-B-n InAs/GaSb superlattice infrared photodetector identified by photoresponse spectra” in Appl. Phys. Lett 95, 102106 (2009) describes work by the University of New Mexico using T2SLs. The use of InAs/GaSb T2SL materials for dual band detectors is described by A. Khoshakhlagh et al., “Bias dependent dual band response from InAs/GaInSb type II strain layer superlattice detectors”, APPLIED PHYSICS LETTERS 91, 263504 —2007. A method for producing a single-bump, dual-band detector for LWIR and VLWIR devices using pNp or n-p-B-p-n T2SL is described by Northwestern University in Applied Physics Letter 92, 111112 (2008).
What is needed is a dual band detector and method of making a dual band detector that is cost effective and that can be scaled up to greater than 4 k×4 k FPA formats, while providing HgCdTe-like performance. Also needed is a dual band detector that allows for elevated temperature operation, which is essential for large format FPAs in order to minimize the size, weight and power footprint of an infrared (IR) imaging system. The embodiments of the present disclosure answer these and other needs.